Methodologies for Frequency Stability Assessment in Low Inertia Power Systems

L'abstract è presente nell'allegato / the abstract is in the attachmen

Frequency Models and Control in Normal Operation: the Sardinia Case Study

Frequency signal is an indicator of the unbalance between the power generation and the load demand. Frequency power reserves in different timeframes are commonly deployed to keep this signal inside strict ranges around the nominal value. Reserves must be carefully dimensioned, and their dynamic performance correctly evaluated to enhance system security. This paper proposes a novel methodology to reproduce frequency fluctuations of entire days and to compute the power reserves activation dynamics by using a two-step process. Firstly, given a real power system frequency signal, a reverse aggregate model provides the unbalance in the system. Secondly, this unbalance is used to recreate and validate the original frequency signal by a forward aggregate model. After this procedure, Battery Energy Storage Systems (BESSs) are added and their impact on the frequency signal is quantified, in terms of different control schemes. The proposed method is tested in the real case of the Sardinian power system. Results show that this methodology can provide accurate estimation of the unbalance, frequency and reserves in the system, giving an understanding of the BESS impact on the frequency control

Frequency Stability of the European Interconnected Power System Under Grid Splitting in Market Zones

This paper proposes a graph theory-based approach to define the possible separation of the market zones in large power systems. The market zone partitioning is used to assess the frequency stability based on a set of parameters, including the inertia, the running capacity of the separated areas, and the power exchanged on the interconnection lines. A system split indicator is finally used to rank the worst split lines. The methodology has been tested on real scenarios of the interconnected Continental Europe power system

Technical and Economic Impact of the Inertia Constraints on Power Plant Unit Commitment

The whole interconnected European network is involved in the energy transition towards power systems based on renewable power electronics interfaced generation. In this context, the major concerns for both network planning and operation are the inertia reduction and the frequency control due to the progressive decommissioning of thermal power plants with synchronous generators. This paper investigates the impact of different frequency control constraints on the unit commitment of power plants resulting from market simulations. The market outputs are compared in terms of system costs, and of frequency stability performance evaluated on the basis of the rate of change of frequency and the maximum frequency excursion. The best compromise solution is found using a multiple-criteria decision analysis method, depending on the choice of the decision maker’s weighting factors. The proposed approach is tested on a real case taken from one of the most relevant future scenarios of the Italian transmission system operator. The results show how the best compromise solution that can be found depends on the decision maker preference towards cost-based or frequency stability-based criteria

The immediate impacts of COVID-19 on European electricity systems: a first assessment and lessons learned

The worldwide spread of the COVID-19 pandemic in 2020 forced most countries to intervene with policies and actions—including lockdowns, social-distancing and smart working measures—aimed at mitigating the health system and socio-economic disruption risks. The electricity sector was impacted as well, with performance largely reflecting the changes in the industrial and commercial sectors operations and in the social behavior patterns. The most immediate consequences concerned the power demand profiles, the generation mix composition and the electricity price trends. As a matter of fact, the electricity sectors experienced a foretaste of the future, with higher renewable energy penetration and concerns for security of supply. This paper presents a systemic approach toward assessing the impacts of the COVID-19 pandemic on the power sector. This is aimed at supporting decision making—particularly for policy makers, regulators, and system operators—by quantifying shorter term effects and identifying longer term impacts of the pandemic waves on the power system. Various metrics are defined in different areas—system operation, security, and electricity markets—to quantify those impacts. The methodology is finally applied to the European power system to produce a comparative assessment of the effects of the lockdown in the European context

Impatti tecno-economici della pandemia da COVID-19 sul sistema elettrico italiano

In questo articolo si analizzano gli effetti del lockdown successivo alla diffusione della pandemia da COVID-19 sul sistema elettrico italiano, dalla riduzione della domanda fino agli impatti economici sui mercati e alle strategie operative adottate